TB-500

TB-500 is a synthetic peptide corresponding to the active region of thymosin beta-4 (Tβ4), a 43-amino-acid actin-binding protein expressed in most mammalian tissues. The synthetic TB-500 is a 7-amino-acid acetylated fragment (Ac-LKKTETQ) corresponding to residues 17–23 of the parent thymosin beta-4 protein. (The "17" in some product literature is the starting residue position, not the peptide length.) The fragment reproduces the actin-sequestering and cell-migration-promoting activity of the parent protein.

Peppudex card: see the mechanism + evidence-grade summary at [Peppudex / TB-500](https://peppudex.com/peptides/tb-500).

Overview

Thymosin beta-4 was first isolated from calf thymus in 1981 by Allan Goldstein at George Washington University. TB-500 is the synthetic fragment most commonly used in research because it retains the biological activity at a fraction of the manufacturing cost of full-length Tβ4. Lyophilized TB-500 is stable at room temperature for short periods and at –20 °C for indefinite storage.

Mechanism

The fragment binds G-actin, sequestering it from the cytoskeletal F-actin pool. This shifts intracellular actin equilibrium toward enhanced cell migration, particularly endothelial cells and stem-cell populations involved in tissue repair. Downstream effects include:

• Upregulation of VEGF and accelerated angiogenesis
• Recruitment of endogenous stem cells to injury sites
• Anti-inflammatory action via downregulation of NF-κB signaling
• Promotion of laminin-5 deposition in epithelial healing

See: Actin, VEGF, Stem_cell_recruitment.

Evidence

Animal-model evidence in cardiac, dermal, and corneal injury is extensive. Notable readouts:

• Myocardial infarction model · reduced infarct size, improved ejection fraction in mice (Bock-Marquette et al., 2004, PMID 15565145)
• Corneal scrape wound · accelerated re-epithelialization in rat corneas and human epithelial cells in vitro (Sosne et al., 2001, PMID 11311052)
• Dermal wound healing · accelerated closure in db/db diabetic and aged mice (Philp et al., 2003, PMID 12581423)

Human clinical evidence is limited to small-cohort studies in cardiac, ophthalmic, and dermal contexts. RegeneRx Biopharmaceuticals has run phase II trials for full-length Tβ4 in dry-eye disease and venous stasis ulcers · TB-500 specifically has no completed phase III data.

Dosing literature

Animal studies used 1–6 mg/kg via intraperitoneal or subcutaneous injection. Community-reported research dose range is 2–10 mg per week, often split across 2–3 administrations. Stacks commonly pair TB-500 with BPC-157 for tendon and soft-tissue recovery protocols.

Storage

Lyophilized: 4 °C for up to 24 months, –20 °C indefinite. Reconstituted: 2–8 °C, use within 28 days. See Reconstitution for prep math.

Regulatory status

• United States. Research use only · not FDA-approved for human therapeutic use.
• WADA. Thymosin beta-4 and its derivatives, including TB-500, were named explicitly under Section S2 (Peptide Hormones, Growth Factors, Related Substances and Mimetics) in the [2018 Prohibited List update](https://www.usada.org/athlete-advisory/2018-prohibited-list-summary-of-major-changes/) and remain prohibited at all times. Reported in equestrian sport doping cases.

See also

• BPC-157 · standard tendon-recovery stack partner
• Reconstitution
• Thymosin_beta-4 · the parent protein
• [Peppudex card · TB-500](https://peppudex.com/peptides/tb-500) · mechanism, evidence grades A-F, FAQs, peer-reviewed sources

References

• Goldstein AL, Hannappel E, Kleinman HK. "Thymosin beta-4: actin-sequestering protein moonlights to repair injured tissues." Trends Mol Med. 2005;11(9):421-9. PMID 16099219.
• Bock-Marquette I, et al. "Thymosin beta-4 activates integrin-linked kinase and promotes cardiac cell migration, survival and cardiac repair." Nature. 2004;432(7016):466-72. PMID 15565145.
• Sosne G, et al. "Thymosin beta 4 promotes corneal wound healing and modulates inflammatory mediators in vivo." Exp Eye Res. 2001;72(5):605-8. PMID 11311052.
• Philp D, et al. "Thymosin beta4 promotes dermal wound repair in aged and diabetic mice." Wound Repair Regen. 2003;11(1):19-24. PMID 12581423.